Anchor rod supporting is a main coal seam roadway supporting method, and can significantly improve the stress state of the surrounding rock of a roadway, improve supporting effect, reduce supporting cost, reduce workers labor intensity, and provide an effective guarantee for safe coal production. A conventional anchor rod is made of a screw-thread steel bar with a nut tray; the anchoring method is to drill a hole with a drill rod first, and then withdraw the drill rod from the hole, charge a resin anchoring agent and insert an anchor rod body into the hole sequentially, stir the resin anchoring agent with the anchor rod to generate anchoring force, and then pre-tighten up.
The conventional anchor rod and the anchoring method thereof have many problems, especially in soft and weak coal rock mass, including: (1) a hole must be additionally drilled out with a drill rod, the drill rod must be withdrawn, and then a resin anchoring agent must be charged and an anchor rod body must be inserted into the hole sequentially, resulting in more steps and waste of time; (2) the anchor rod body is a single rigid rod body, the length of the anchor rod body cannot exceed the maximum diameter of cross section of the roadway; consequently, the length of the anchor rod body often cannot meet the design requirement owing to limitation of roadway dimensions; (3) in soft and weak coal rock mass, the resin anchoring agent has poor adhesion to the loose and cracked coal rock mass, resulting in inadequate anchor bonding force; (4) the hole drilled out in soft and weak coal rock mass shrinks and deforms quickly; as a result, it may be impossible for the resin anchoring agent to be charged or the anchor rod body to be inserted into the hole, resulting in an abandoned hole. Those problems severely limit the use of anchor rod supporting technique for supporting soft and weak coal rocks.
A variety of novel anchor rods have been developed, including self-drilling and self-anchoring anchor rods and extendable anchor rods. However, among those novel anchor rods, self-drilling and self-anchoring anchor rods do not have an extension function, while extendable anchor rods do not have a self-drilling and self-anchoring function, or the anchoring method thereof is unsuitable for soft and weak coal rock mass. There is an urgent need for a novel anchor rod and a novel anchoring method that can fully overcome the above-mentioned problems.